With popularization of smart phones and rapid development of mobile internet technologies, a problem of network capacity and base station deployment is becoming more and more serious. Capacity expansion based on a macro station may render site selection of a base station and engineering construction more and more difficult, and may lead to higher and higher costs, and therefore, miniaturization, low power consumption, controllability and intelligentization of a base station device have already become a mainstream trend. Hereto, a series of miniaturized base stations, namely small base stations, including a femtocell (Femtocell), a picocell (Picocell) and a microcell (Microcell) and so on, has been launched on the industry chain simultaneously, and all these technologies can be called small cell (Small Cell) technology. A Small Cell is a wireless access point with low power, which may cover a range of 10 meters to 200 meters, and being compared with a macro station, a characteristic of the Small Cell is that it may improve indoor coverage depth, increase network capacity and lift user experience etc. In deployment of a long term evolution (Long Term Evolution, LTE for short) system, in order to support more users and higher system capacity, many small base stations may be deployed within the coverage of a macro cell. At present, the LTE system is designed aiming at macro cells, and channels and signals in the system should satisfy the macro coverage. But for the Small Cell, how to provide higher bandwidth, better performance and lower costs according to its characteristics is a problem that needs to be considered urgently.
Any cellular system has a basic requirement that a terminal needs to have a possibility of applying for establishing a network connection, which is usually referred to as random access. One step in a random access process is that a user equipment (User Equipment, UE for short) transmits a random access preamble (preamble) signal, and a base station performs timing estimation based on this signal, thereby realizing uplink synchronization. Duration of the preamble signal relates to a coverage range of a cell, and the bigger the coverage range is, the longer the duration of the preamble signal gets. In the present LTE system, preamble signals are all relatively long, where preamble format 0 lasts for about 1 millisecond (ms), supporting coverage up to 14 kilometers, preamble format 1 lasts for about 2 ms, supporting coverage up to 77 kilometers, preamble format 2 lasts for about 2 ms, supporting coverage up to 29 kilometers, and preamble format 3 lasts for about 3 ms, supporting coverage up to 100 kilometers. But for a Small Cell, preamble signals of these formats are all relatively long, which is a waste of resources.